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#!/usr/bin/perl -ws
use Parse::RecDescent;
$RD_AUTOACTION = q{ $item[-1]; # JUST TO SHOW THEY WORK WITH PRECOMPILED PARSERS
};
Parse::RecDescent->Precompile(<<'EndGrammar', "Calc", $0 );
{ use Coy; }
{ my $lexical_var = 1; }
mult_op: '*' { sub { $_[0] *= $_[1] } }
| '/' { sub { $_[0] /= $_[1] } }
main: expr /\s*\Z/ { $lexical_var++ } { $item[1]->() }
| <error>
expr: /for(each)?/ lvar range expr
{ my ($vname,$expr) = @item[2,4];
my ($from, $to) = @{$item[3]};
sub { my $val;
no strict "refs";
for $$vname ($from->()..$to->())
{ $val = $expr->() }
return $val;
}
}
| lvar '=' addition
{ my ($vname, $expr) = @item[1,3];
sub { no strict 'refs'; $$vname = $expr->() }
}
| addition
range: "(" expr ".." expr ")"
{ [ @item[2,4] ] }
addition: <leftop:multiplication add_op multiplication>
{ my $add = $item[1]; sub { ::evalop($add) } }
add_op: '+' { sub { $_[0] += $_[1] } }
| '-' { sub { $_[0] -= $_[1] } }
multiplication: <leftop:factor mult_op factor>
{ my $mult = $item[1]; sub { ::evalop($mult) } }
factor: number
| rvar
| '(' expr ')' { $item[2] }
number: /[-+]?\d+(\.\d+)?/ { sub { $item[1] } }
lvar: /\$([a-z]\w*)/ { $1 }
rvar: lvar { sub { no strict 'refs'; ${$item[1]} } }
EndGrammar